Vasoconstriction and vasodilation are essential to blood pressure regulation and physiological responses in health and disease. Vascular contractility can be measured in humans in vivo and in animals ex vivo. Unfortunately human studies require a skilled technician and have limited ability to vary physiological stimuli, whereas animal studies are time consuming and may have limited applicability to human vascular function. While attempts have been made to develop in vitro systems to measure vasoconstriction and vasodilation, these systems do not include circumferentially aligned primary human vascular smooth muscle cells (vSMC) nor do they include perivascular adipose tissue (PVAT), which is critical to arterial response to vasoactive stimuli. Our long-term goal is to understand how PVAT affects arterial function in health and disease. The goal of this project is to create an artery-on-a-chip which includes PVAT and enables vasoconstriction and vasorelaxation measurements in response to both mechanical and biochemical stimuli. As an integral part of the iterative design process, we will thoroughly verify the in vitro artery-on-a-chip via ex vivo pressure myography of mouse resistance vessels and through comparisons to human studies. The artery-on-a-chip does not have to recapitulate all arterial structures (e.g., elastic lamina) or mechanical properties (e.g., burst strength); it only needs to demonstrate similar vasoconstriction and vasorelaxation trends to native arteries. To support the creation of the artery-on-a-chip with PVAT, we propose the following aims: Aim 1: Create an endothelialized tube of circumferentially aligned, contractile vSMCs We will use microribbons to circumferentially align vSMC in a cylindrical hydrogel channel and fluid flow to axially align endothelial cells (EC). We will determine how hydrogel composition and mechanical properties affects vSMC alignment as well as artery-on-a-chip vasoconstriction and vasodilation. Aim 2: Incorporate perivascular adipose tissue (PVAT) around the engineered vessel We will test which PVAT source and incorporation method best recapitulates PVAT effects on vasoconstriction and vasodilation in healthy and inflamed conditions in the artery-on-a-chip. Aim 3: Validate artery-on-a-chip with ex vivo pressure myography and in vivo human data We will thoroughly validate the artery-on-a-chip with PVAT by comparing it to ex vivo pressure myography of mouse vessels and in vivo human vasoreactivity data in healthy, inflamed, and obese conditions. This research will be the first to create a human artery-on-a-chip with PVAT to test vascular contractility. The device will have implications in drug testing as well as in elucidating mechanisms through which PVAT affects vascular function. In addition, the novel biofabrication methods will be applicable to other 3D aligned cell cultures.